It exist systems for preparing beverages such as coffee by forcing a liquid through the substance contained in the capsule using centrifugal forces.
WO 2008/148604 for example relates to a capsule for preparing a beverage or liquid food from a substance, in a centrifugal brewing unit, by passing water through the substance contained in the capsule by using brewing centrifugal forces comprising: an enclosure containing a predetermined dose of substance; opening means which opens under the centrifugal effect to allow the brewed liquid to leave the capsule. The capsule may also comprises means for engaging the capsule to external rotational driving means of a centrifugal brewing device wherein the engaging means are configured to offer a resistance to torque during rotation of the capsule for maintaining the capsule in a reference rotational position.
Thereby, the effect of centrifugal forces to brew coffee or prepare other food substances presents many advantages compared to the normal brewing methods using pressure pumps. For example, in traditional espresso or lungo coffee type brewing methods using a pressure pump, it is very difficult to master all the parameters which influence the quality of extraction of delivered coffee extract. These parameters are typically the pressure, the flow rate which decreases with the pressure, the compaction of the coffee powder which also influences the flow characteristics and which depends on the coffee ground particle size, the temperature, the water flow distribution and so on. Therefore, it is not easy to vary the extraction pressure and flow rates because there are essentially determined by the resistance of the bed of coffee and the downstream filtering system.
For a centrifugal extraction, the quality of the beverage to be prepared (intensity or strength, taste, aroma, foam/crema, etc.) is complex and depends on the control of different brewing parameters and capsule design. In particular, the flow rate of the injected liquid in the capsule seems to play an important role. The flow rate can be influenced by a number of parameters such as the rotational speed of the capsule in the device, the fluid dynamics inside the capsule, the back-pressure exerted on the centrifuged liquid. For instance, for a given back-pressure, the higher the rotational speed, the larger the flow rate. Conversely, for a given rotational speed, the larger the back-pressure, the smaller the flow.
Whereas the rotational speed of the capsule is usually controlled by control means selectively activating a rotational motor of a centrifugal beverage production device, a predefined back-pressure is preferably obtained by a flow restriction at the outlet of the capsule or at the outside of a centrifugal cell carrying the capsule.
For example EP 651 963 teaches that a pressure gradient is obtained by a rubber-elastic element interposed at the interface between the lid and the cup of the centrifugal cell, e.g., a capsule containing coffee powder. Such an element deforms elastically to leave a filtering passage for the liquid when a certain pressure is attained at the interface.
Furthermore, documents FR 2 487 661 and WO 2006/112691 relate to centrifugal systems wherein a fixed restriction is placed downstream of the filter to create a pressure gradient.
Moreover, WO 2008/148646 proposes a solution in which a flow restriction is placed in or outside the centrifugal cell. The flow restriction can comprise a regulating valve offering an effective pressure. The valve opens under the effect of pressure. The more the valve opens, the higher the flow rate. The valve can be preloaded by a resilient element (rubber or spring).
EP-A-1849715 relates to a capsule for the preparation of a beverage with a sealing member attached thereto and comprising a crimping portion of the flange-like rim for the sealing member forming a curled end. However, such capsule is not designed for delivering a beverage, e.g., coffee extract, by centrifugal extraction.
The prior art centrifugal beverage production systems however suffer from the drawback that an adaptation of the back-pressure to predefined values either requires a mechanism that makes it complex to adjust to a large variety of different predefined values of the back-pressure.
Thereby, it is to be understood that in particular with respect to coffee beverages, the back-pressure applied on the centrifuged liquid determines the extraction conditions (e.g., flow rate) thereby influencing directly the coffee taste and aroma. Furthermore, the organoleptic texture such as the foam/crema formed on top of the prepared beverage highly also depends on the applied back-pressure. Thus, with respect to the foam/crema as well as the flow rate of a coffee beverage to be prepared, it is desired to adjust the values of the back-pressure dependent on the nature of the ingredient provided in a specific capsule as for different types of beverages a different quality and/or quantity of the foam/crema respectively a different flow rate is desired.
Therefore, there is a need for proposing a new centrifugal capsule system for which the back-pressure exerted on the centrifuged at the interface between the capsule and the device can be better and more independently controlled for improving quality of the delivered food liquid.
The term “back-pressure of the valve means” refers to the pressure loss created by the restriction or restriction valve. As the restriction or restriction valve forms a “bottleneck effect”, a pressure of liquid is created upstream of it by the effect of the centrifugation. Thanks to this restriction, the pressure before the restriction is increased, and it is this pressure which has an effect on the liquid-ingredients interaction (e.g. by extraction of the ingredients by the liquid). This pressure created by the restriction valve can also be defined as the ratio of force (“back-force”) divided by the area of surface contact at the restriction valve.
Co-pending European patent application No. 08171069.1 proposes a capsule on which a force ring is provided that is engaged by a pressing surface of the beverage preparation device to form a valve means which provides, under the force of resilient means associated to the pressing surface, and depending on the height or thickness of the force ring, a certain back-pressure during beverage extraction.
The present invention provides an improved solution to the capsule of European patent application No. 08171069.1, in particular, a capsule that resists deformation under the compressive forces applied by the pressing surface of the device onto the force ring for a better control of the back-pressure. The proposed solution is also economical and can be reliably produced in mass production with a high respect of the dimensional tolerances. Furthermore, the proposed solution also allows the use of materials providing high gas barrier properties, e.g., aluminium, without need for additional elements on the capsule therefore providing a relatively simple capsule.
The present invention provides a solution to the before-mentioned problems as well as offers additional benefits to the existing art.